Tube tester



March 30,- 1937. R. WILLIAMS TUBE TESTER Filed June lO, 1951 PatentedMar. 30, 1937 TUBE TESTER Jewell R. Williams, Little Rock, Ark.,assignor, by mesne assignments, to Jerry H. Glenn, Little Rock, Ark.

Application June lo, 1931, serial No. aimiez.Y

9 Claims.

This invention relates to testing apparatus and methods for use indetermining the various conditions of vacuum tubes such as those used inradio receiving and transmitting sets, and for various other purposes.

It is a general object of the present invention to provide novel methodsof and apparatus for testing vacuum tubes. y

In particular, it is an object of the invention to provide a vacuum tubetesting apparatus operated entirely by alternating current.

A further object of the invention consists in the provision of apparatusfor testing vacuum tubes in which a single meter is used both for l5determining the testing voltage and for indicating various conditions ofthe tubes being tested.

An important feature of the invention resides in the provision of aplurality of shunts adapted to be selectively associated with the meterand so adjusted in capacity that for every test the meter will give thesame indication for tubes of various characteristics which have the sameconditions.

Another important feature of the invention resides in the means forselecting the proper filament voltage for the tube and for consequentautomatic selection of a shunt to be used when testing the tube with apositive or negative grid bias.

:lo Another feature of the invention resides in the use of a rectier andmultiplier which permit the voltage of the transformer secondary to beproperly adjusted to insure uniformity of results by noting the voltagethereof on the direct cur- .33 rent meter used in the set.

Another important feature of the invention resides in the manner oftesting for short-circuits between the elements of vacuum tubes whereina pilot lamp is provided in the plate circuit to in- -il dicate such afaulty condition of the tube and to limit the flow of plate current fromthe transformer to a safe value.

Another feature of the invention resides in the circuit arrangements andthe provision of a pluralitylof switches for automatically placing thetubes'in successive circuit arrangement for testing under variousconditions and in which a single operator progressively actuates thevarious switches and maintains each prior operated one in its operatedcondition as it moves to succeeding switches to operate them.

Another important feature of the invention resides in the provision of aseparate grid biasing secondary so arrangedgthat alternating current inphase or counterphase to the plate current can be applied to the tubegrid at will for assisting in determining the characteristic of the tubeand in which under all conditions the same grid bias is availableindependent of the filament voltage.

Other and further features and objects of the (Cl. Z-27) invention willbe more apparent to those skilled*V Y in the art upon a consideration ofthe accompanying drawing and following specification,

wherein are disclosed several exemplary embodiments of the inventionwith the understanding.

apparatus for carrying out the lnethod of the present invention; and

Figure 2 is a detail of the multiple switch used,

for connecting the lament to the proper potential and for associatingthe proper shunts with the meter.

In the testing of vacuum tubes and particular.- 1y those used for radioreceiving sets, it is highly desirable to provide suitable apparatuswhereby tests may be conducted by those with a limited knowledge ofelectricity, and this apparatus should be as simple and fool proof aspossible..

In order to perm-it testing apparatus to be extremely simple, thepresent invention has been devised which makes use of a mini-mum numberof parts and yet permits complete and accurate testing of a largenum-ber of tube types for all of the characteristics necessary to beknown, for the ordinary testing of such tubes for general usage.

The present Yinvention is disclosed diagrammatically for convenience inillustrations and description but it will, of course, be understood thatit can be embodied in any desired form, preferably enclosed in asuitable cabinet for use on a counter or in a case for convenientcarrying. The exact embodiment of the invention forms no part of thepresent invention and is in no sense limiting. y

In order that the device be as simple as possible, it is constructed tooperate solely from a suitable source of alternating current whichprovides all of the testing potentials. The essential parts of theapparatus then comprise the transformer Iii, a plurality of tube socketsI I, a meter I2, suitable circuit associating wiring, and a group ofswitches i3. The sockets are indicated by the usual diagrammatic showingfor. vacuum tubes in order to indicate the types of tubes which areintendedto be inserted therein. Four of these sockets are indicatedthough it is obvious that any desired number could be provided andsuitably connected. The socket numbered I4 is for use with four elementtubes of the screen grid type using `direct current on the filament. Thesocket numbered I5 is for alternating current screen grid tubes in whichthere is a heater and a separate' emission element. The socket numberedI6 represents the usual three element direct or alternating current tubeand the socket numbered l1 is for the four element type of alternatingcurrent tube using a separate heater and emission element.

5 All of the potentials for testing are provided by the transformer l0which` has the primary winding i8 having in series therewith the ballastresistor i9 of the variable type. Suitable alternating current of any ofthe available potentials 10 between 85 and 135 volts is adapted to beapplied between the terminals 2U, 2| and by adjustment i of the ballastresistor provide the desired output potential for testing.

The transformer has four independent secondary windings, that numbered22 providing the plate and screen grid potentials, that numbered 23providing lament current for the rectier tube, later to be described,that numbered 24 being a tapped secondary to provide various potentialsfor filament lighting and that numbered 25 being a grid-bias secondarywinding.

In order that the voltage of the secondary winding 22, or, in fact, anyother of the windings of the transformer may be accurately measured and25 adjusted so that all testing may take place at the same potential,means are provided whereby the meter |2 may be used for the purpose.This meter is a conventional direct current milliammeter of one milfull-scale capacity. To adapt it to measure alternating currents asuitable rectifier such as the tube 25 is provided, having the lament 21connected by the conductors 28 to the Winding 23 and having the plate 29connected by the conductors 30 and 3| to the 'negative terminal 32 ofthe meter. The positive terminal 33 of the meter is connected by theconductor 34 to the left hand end of the secondary 22. The circuit formeasuring the voltage of this secondary is completed by the commonconductor 35 which connects the right end of the secondary 22 to thefilament secondary 23 thereby completing the circuit and permitting thevoltage of the secondary to be adjusted by manipulation of the ballastresistor I9. It may be necessary to place a multiplier 36 in the circuitto insure the reading within the range of the meter and preferably themeter is provided with a center line 31 and a suitable legend on theface instructing the operator to adjust the ballast until the needlereaches this line, when the apparatus is in condition for testing.Preferably, the transformer is so wound that a voltage of 150 isdelivered by the secondary 22 when S5 volts is effective across theprimary i8 and it is the intent to have the resistor adjusted to providethis effective voltage.

The remainder of the apparatus and circuits can best be described bycarrying through the series of tests permitted by the apparatus.Suppose, for instance, that a vacuum tube of the type known as U X 261 Abe placed in the socket i6, it will be seen that its ilament 40 willhave one of its terminals connected by the wire 4| to the movable switcharm 42 which is adapted to range over a group of contacts suitablyarranged in an arc and connected by the conductors indicated to thevarious taps on the secondary 24. The rst group of contacts 43 areconnected to the left hand end of the secondary 24 to provide '1l/2volts for tubes whose filaments have this requirement. The next group ofcontacts and those on which the switch arm 42 is shown resting areconnected to the five volt tap etc., in accordance with the requirementsof the various types of tubes. The opposite end of the secondary 24 isconnected to the common return conductor 35 previously mentioned, whichis also secured to the left hand terminal 44 of the rst of the switchesat the lower part of the drawing. The terminal 45 ofthis switch isconnected by the wire 46 to the terminal 41 of the next switch which isshown in contact with the terminal 48 thereof, which is connected bywire 56 tothe opposite terminal of the lament 4B.

Since contacts 44, 45 are disengaged the lament will not be lighted, butplate potential is provided for the tube over the wire 5|, the closedcontacts 52, and 53, wire 54, shunt wires 55, switch arm 55, wire 51,switch contact 58, switch contact 59, wire 6B, to wire 34 and the lefthand en-d of the secondary winding 22. The opposite end of this windingis connected, of course, by the common conductor 35 to the filamentlighting secondary. Under these conditions no current will flow in theplate circuit, because the lament is not lighted, unless there is ashort circuit in the tube between the plate and filament in which casethe closed circuit will cause a ilow from the plate secondary which willlight the iilamcnt of the pilot light 6| in the wire 34, which onbecoming heated, increases its resistance and forms an effectivelimiting means for the current. By a similar tracing of circuits it canbe seen that the same test is effective with a tube placed in any of thesockets.

If there is a short circuit between the plate and the grid a similarindication will be effected in an obvious manner for the current fromthe grid flows over the wire 62 to wire 53, contact 64, contact 65, wire66, contact 61, contact 553, wire 5B, back to the filament and then aspreviously traced to complete the circuit and light the lamp 6|. 1f thetube has no short circuited elements, nothing is indicated and the nexttest can be carried out.

Some radio tubes do not short circuit until the lament has been lightedwhen it expands and contacts with certain of the other elements. Toindicate such a condition, contacts 44 and 45 are closed to complete thecircuit to the lament from the transformer and light the filament aspreviously described. If the heated filament causes a short circuit inthe tube the same indications take place as described in connection withthe unlighted filament circuit. If no indication of short circuit ismade, the tube is then ready to be tested with the negative grid bias.

All of the switches in the line at the bottom of the drawing arearranged to be closed in succession by means of a suitable actuator lilwhich is so arranged that after a switch is closed and the actuatormoves to the next, it retains lclosed all of the preceding switches.

In testing a tube in the socket i6 for its action with a negative gridbias, the actuator 15 moves over the rst switch which closes thefilament circuit and then over the second switch which is intended onlyfor testing tubes with a separate heater and is marked Cathode to heatershort and then passes on to the third switch marked Grid action openingthe contacts 31, 68 and closing the other two contacts thereof. Underthese conditions the meter terminal 32 is connected by the wire 3| tothe switch spring 12 now in contact with the spring 13. The switchcontact 12 is out of engagement with the contact 14 which removes therectier tube from the circuit leaving its filament lighted, however. Theplate circuit of the tube to be tested is now from the left end of thesecondary 22, through the wire 34, through the meter l2, through thewire 3|, to the switch-contact 12, to contact 13, to wire 15,

` phase of the current delivered to the plate.

needle for the various Acurrent flows.

to ycontact 53, to contact 52 vand -wire 5| to the tube plate whichLplaces alternating current on the plate after the lament is lighted.The only current flowing, however, will be the positive half of Veachalternationowing to the rectifying action of the `tube so that adirectvpulsating current flows which ywill actuate the Adirect current meterI2.

'The current from the plate flows through the electrons in the `tube-tothe lament and over the wire 50 tofthe contact 5:8 now separated fromBland-in engagement with Hand 7.8. From contact 11 current ows in thewire-f7.9, to the wire 35 which returns it tothe common conductorbetween the ifilamentand plate secon'daries. This flow of current isgoverned by the -density of the electron flow Yandthe effect of the gridpotential. Negative -voltage on the grid repels the electron flowconsequentlydecreasing the amount of current possible to flow from `theplate tothe lament.

'In order to apply negative potential tothe grid and yet use alternatingcurrent, it is necessary to so phase this current lthat it is counter tothe This is effected bythe secondary winding 2.5, `an intermediate pointof which Iis1cor1nected by the wire 63to the grids of all --of vthetubes. Contact with vthe control grids of the screen grid tubes is bythe flexible conductor and clip 52'. With the windings of allthesecondaries'in the same direction it becomes necessary to use thesection at the left of the intermediate tap and this is connected bywire g8l) to switch contact l'8| in engagement with ncontact 82-connected by Wire y82? feature of this invention resides 'in having themeter read at the same indication for the same condition of tubes having:diiferent plate current capacities and inorder to eiect 'this' result,it is necessary to shunt the Ineter'with various shunts so adjusted asto insure this positioning of the This is efffected automatically `byarranging the shunts in connectionwith contacts concentric with thecontacts for the adjustment of filament voltage and insuring themovement of A'the pointer over these contacts automatically as thefilament voltage vis adjusted. Since there are several tubes using thesame filament Voltage, but which use different plate currents, therewill be a number of taps for the shunts for each set of filament voltagetapsfand in some desirablemannerthe operating mechanism for the movableswitch arms will 'be provided with indicating means so that they can beset for the particular tube being tested and in so setting will providethe proper lament voltage and associate the correct capacity shunt withthe meter.

The meter is preferably devoid of the usual graduated scale and in placethereof has marked thereon Bad-Poor-Fair-Good-Gas. Every vtype of tubein proper condition will give an indication of Good when tested as justdescribed, and the shunts are so arranged as to produce this result.

The shunts in the -outer ring and marked 55 coopenate 4with themeter`when ,makingga ,test with negative .grid biasand these shunts are,connected between 'the contact buttons indicated whicharerengageabletby the switch arm 156 which movesin unison'withthe filamentvoltage switch arm 4&2: V.The :proper value orshunt between the commonlead i5land the various contacts ,is determinedrby tting the propersocket with la laboratory standard tube and adjusting the amount vofshunt until 'the :meter Vreads Good. @wing to the differentcharacteristics cof thevarious typesof ytubes it may not fbe possible toprovide a continuous tapped shunt .as shown :but separate shunts may berequired leading ,from

each Contact to the common terminal 1.54 ras will if be clearlyunderstood. It will be seenithat the shunt will be placed across theterminals of the meter when the third of thesequence 'of switches isclosed, for the wire ,60 leadingfrom the termin-al 33 of the meter isconnected to the switch the `shunt is connected by the A.wire 154, wire.115. 1

contact 513 now in engagement with the contact 12 and wire .3| toterminal 32 of the meter.

` If after calibration some other `tubeis ,placed in the socket and the4shunt set .-as originally calibrated for that type tube the needle'maypoint 1'* to any of the designations onthermeter according tothe ow ofplate current which vis controlled by the condition of the tube. .If thetube has aa gas content the grid cannot repel'electronssas in avacuumand a greater amount `of current will flow-causingthe needle toswingover .to the section of the-scale marked Gassy. The samecalibration procedure is gone through `for :all Vother types of tubes.

The next test to be made `is that of tube .operation when a positive or.in-phase voltage is impressed on the grid and this is done by .movingthe progressive switch operator 10 7to operate the fourth switch markedPlate Action. Moving the fourth switch opens contacts 8l, 82, removingthe left hand end of the grid ,bias usecondary from the circuit. At thesame time 'the opposite end of thiswinding l25 is connected to the twogrids through the wire 84, closed contacts 85, 86, wire 81, contacts 88and 89, now

closed, to wire 'l9 leading to wire 30 and back to the common conductor35. This places on the grid a positive or iii-phase Voltage impressedatthe same time the plate of the tube is positive forthe grid bias sectionof the secondary now in use is wound in the same direction as the platecurrent secondary. When the grid is positive it aids the flow ofelectrons and hence there is v'a greater current owbetween the plate andfilaf irst discussed and the row of contacts for the filament voltage.At one end they are connected to the common conductor 54. They arecalibrated in exactly the same manner as discussed in connection withthe shunts used for the negative grid test. They are placed in circuitas follows: From the terminal .33 of the meter, over the wire S0 to thecontact 59 now closed against contact S9, over the wire 9| to themovable'switch arm 92 for the intermediate row of shunts, then throughthe proper shunt to the wire 54, wire `'1.5,

contact 73, closed to contact 12, and wire 3| to terminal 32 of themeter, thus shunting it with a shunt adjusted in accordance with thetype of tube being tested. As in the previous test any tube of unknownquality can be tested by placing it in the proper socket after theshunts have been properly adjusted by the use of standard tubes. If thetube being tested has a low plate impedance or high mutual conductancethe eieot will be to allow more current to flow than usual and theneedle of the meter will move to the right or past the division markedGood and will show Low mu.

When the device is used for an alternating current type of tube using aseparate heater which heats a cathode to give oir electrons such a tubeis placed in the socket ll and the heater is immediately lighted becauseit will be seen that there is a completed filament circuit thereforthrough the common wire 35 on one side and the wire 53 leading from the21/2 volt tap from the filament transformer. If the tube has an internalshort from plate to other element the same action will take place asdescribed for the four element tubes and the pilot light lights as anindicator. The tube has already been heated so it is not necessary tohesitate with the progressive switch operator on the first switch. Ii noshort is indicated, the shunt rotor is rotated until its pointerindicates the marking on the panel for the heater type tube being used.

Heater type tubes sometimes have a short between the cathode 94 and theheater 95. If such a short occurs it is determined by moving theprogressive switch operator so the Cathode to heater short contacts areactuated. This removes the rectier from the circuit as previouslydescribed and connects the terminal 32 of the meter to the wire 'l5which leads to the wire 54 connecting to the common point of the shunts.The wire 54 through the contacts 55 and 52 and the wire 5| is connectedto the plate of the tube. The terminal S3 of the meter is connected bythe wire 5U, the contacts 59 and 58 and the wire 5l to the movablecontact 56 on the outer row of shunts. This terminal is also connectedby the wire 34 to the left hand end of the plate secondary Q2 whichplaces potential on the plate. The circuit is not closed, however, sothat there can be a flow and indication on the meter because there is nolament in the tube and the heater which is connected to the lamentwinding and would normally provide the return through the common ground35 does not receive the flow of electrons which travel to the cathode 94and this is normally out of contact with the Aheater and with the commonground as can be seen by tracing its wire 5@ to the open contactsbetween the springs 'il and 58. If, however, there should be a shortbetween the heater and the cathode, then the circuit would be closed andan indication on the meter would be a showing of a short circuit betweenthese elements.

If there is no such indication, the tests for grid action and plateaction are carried out the same as explained in connection with tubes inthe socket numbered I6.

Two sockets are provided for screen grid tubes,

`one I4 for the direct current type and one I5 for the alternatingcurrent type using a cathode and heater. By using separate sockets forthese tubes because of the connection of the screen grid to the socketterminal normally connected to the control grid of other tubes,complicated switches are eliminated. It has already been explained thatthe control grid is connected by the clip |52 secured to the cap 95 atthe top of the tube.

In` testing these screen grid tubes, the test differs only from thecorresponding test for the same type tube without the screen grid, inthe furnishing of a screen grid voltage in phase with the plate voltagebut of a lower potential, and this is readily accomplished by tappingoff the plate voltage secondary at an intermediate point 5l and runningthe wire 93 to the screen grids 99. The calibrations for the shunts forthese tubes and the tests are conducted in the same manner as describedheretofore and the screen grid positive potential governs any changes incalibration so that the indications are the same as with the other typetubes.

In order to provide for testing filament type rectiers such as thosewith two plates giving full wave rectication and those with one plategiving half wave rectication, these tubes are used with the socket I5.We will consider only the full wave rectification tubes since the testfor one plate in that type tube would be identical with the test for ahalf wave rectifier tube.

The test for a rectier tube is the current 'flow from plate to filamentwhich is in turn demally connected to the shunt 55 by the common wire54, the contact 53, contact 52, wire 5| -to the plate. The meter isconnected to the shunt as described in connection with the plate testwith positive potential on the grid. The movable contact 92 for theintermediate shunt is adjusted to the proper position for the tube beingtested and if the shunt has been previouslyr properly calibrated thequality of the tube will be indicated by one of the indicia on the meterface.

In order to read the current iiow from the other plate of a full waverectier, it must be remembered that its socket prong is received in thesocket contact which is normally connected to the grid wire 62 but bymoving the progressive switch to open the contacts 52, 53 and close 53,|02 this grid wire 62, 53 is transferred into contact with the wire 5dwhich leads to one end of the shunt and therefore the plate in therectifier tube is properly connected to the meter in order that thecurrent flow to the plate can be determined.

In Figure 2 is seen schematically an arrangement for the three movablearms, 42 for the laments; 92 for the shunts for plate current withpositive grid bias; and 56 for plate current measurement with negativegrid bias. They can be mounted on and insulated from a single shaft |65which can be rotated so that the pointer |06 swings over a scale havingindicia thereon indicating the various tubes.

The actuator lil for the progressive switch is preferably biased by aspring |07 to always return to the off position so that before each tubeis tested there is an assurance that the switches are in normal positionand will pass progressively to the various positions for the propersequence of tests.

The provision of the adjustable shunts makes this testing apparatushighly desirable in that it provides a scale on the meter which can beread by those unskilled in the electrical art and permits tubes to beproperly tested by any one who can read. No knowledge is needed of thedesired amount of plate current for the various type tubes, for any tubetested in this apparatus will give an indication on the meter of itsexact condition in language readily understood. It will be appreciatedthat details of construction can be varied to suit the conditions andhave no bearing on th-e main features of the invention.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

l. In a vacuum tube tester in combination, a transformer having filamentlighting means tapped for various tube iilaments, and a plate excitingmeans, grid biasing means, a tube socket, circuits associating saidmeans and socket, a milliammeter in the plate circuit, a plurality ofshunts for said meter, means to concurrently adjust the filament voltagefor the type tube being tested and connect a shunt to the meter suchthat the meter gives the same indication for similar conditions of alltypes of tubes.

2. In a vacuum tube tester in combination, a transformer having afilament lighting secondary tapped for various tube filaments, a plateexciting secondary and a grid biasing secondary, a tube socket, circuitsassociating said windings and socket, a milliammeter in the platecircuit, a plurality of shunts for said meter, means to concurrentlyadjust the filament voltage for the type of tube being tested, andconnect a shunt to the meter such that the meter gives the sameindication for similar conditions of all types of tubes, and means toapply current from the grid biasing secondary to the tube grid in phasewith the plate current and out of phase therewith at will.

3. In a vacuum tube tester, in combination, a transformer having afilament lighting secondary tapped for various tube iilament voltages, aplate current secondary and a grid biasing secondary, a tube socket,circuits associating said socket and secondaries and including a platecurrent milliammeter, two sets oi" shunts for said meter, means toselect the proper filament tap for the type tube to be tested, meansautomatically actuated upon said selection to select two shunts for usewith said meter, means to connect said bias secondary to the grid incounter phase to the plate current and to connect one of said shunts tothe meter and means to connect said bias secondary to the grid in phasewith the plate current and to connect the other selected shunt to themeter, each shunt being selected for its respective type of tube to giveidentical readings for all tubes of like condition and for both gridbias conditions.

4. In a vacuum tube tester, in combination, a plurality of tube socketsfor different type tubes, a transformer having a primary winding, atapped lament lighting secondary, a plate current secondary, and aseparate grid bias secondary, a meter, a plurality of circuitsassociating the tube sockets, secondaries and meter, a plurality ofswitches to variously associate said parts and circuits for a series oftests of a tube in the socket, said switches being arranged to close thecircuits in sequence to effect the tests in a denite order, and means tosuccessively close and hold closed the switches.

5. In a vacuum tube tester, in combination, a multiple switch includinga iilament Voltage adjusting means having several positions for eachlament voltage, and a meter shunt selecting means automatically movedwith the filament voltage adjusting means to select a shunt for aparticular tube for each position of the filament voltage adjustingmeans.

6. The method of testing vacuum tubes of different characteristics in atester including a source of adjustable alternating filament potential,a source of alternating plate potential, a source of grid potential, ameasuring instrument, and an adjustable shunt, comprising energizing thetube iilament at the proper potential, applying the plate potentialthereto, inserting the measuring instrument in the plate circuit, eX-citing the grid from its source of potential, inserting the shunt inparallel to the instrument and adjusting it to a predetermined Value forthe particular tube, and noting the deviation of the instrument from aiixed indication for all types of tubes.

7. The method of testing vacuum tubes of different characteristics in atester including a source of adjustable alternating filament potential,a source of alternating plate potential, a source of alternating gridpotential, a measuring instrument, and an adjustable shunt, comprisingenergizing the tube lament at the proper potential, applying the platepotential thereto, inserting the measuring instrument in the platecircuit, exciting the grid from its source of potential in phaseopposition to the plate potential, inserting the shunt in parallel tothe instrument and adjusting it to a predetermined Value for theparticular tube, and noting the deviation of the instrument from a iiXedindication for all types oi" tubes.

8. The method of testing vacuum tubes of different characteristics in atester including a source of adjustable alternating lament potential, asource of alternating plate potential, a source of alternating gridpotential, a measuring instrument, and an adjustable shunt, comprisingenergizing the Atube filament at the proper potential, applying theplate potential thereto, inserting the measuring instrument in the platecircuit, exciting the grid from its source of potential in phase withthe plate potential, inserting the shunt in parallel to the instrumentand `adjusting it to a predetermined value for the particular tube, andnoting the deviation of the instrument from a iiXed indication for alltypes of tubes.

9. In an audion tube tester; the combination with a normallyde-energized transformer having its primary and secondary windingsarranged to deliver voltages of various iixed values; of an electricalnetwork; a plurality of selector switches connected in the network andto the transformer and to the elements oi an audion tube; an electricalmeasuring means connected in said network; a single manipulative devicesimultaneously to set all of the selector switches thereby applying theproper voltage to each element of said tube; and means to energize thetransformer and to alternately impress diierent voltages on a certainone of the tube elements to test the electrical condition of saidelement.

JEWELL R. WILLIAMS.

